Dumb question ... what's your logwarn returning? If it returns a true value you continue on to the next condition ...

if
  ( change current dir OR log error ) AND
...
if
  ( 0 OR 1 ) AND
...

if( 1 ) AND 
...
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Personally, I would wrap the code up in an eval:

eval {
 $ftp->login($data->{'login'}, $data->{'pw'}) or die($ftp->message);
 $ftp->binary or die($ftp->message);
 $ftp->cwd($data->{'remote_dir'}) or die($ftp->message);
 $ftp->put($to_upload) or die($ftp->message);
 $ftp->quit;
};

if( $@ ) {
 $log->error("upload_file: xqe $data->{'id'}, " . $@);
 return undef;
} else {
 return 1;
}
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